Targett, who was previously the founding editor of the Mail on Sunday's Night & Day magazine, resigned from the Observer in July following the appointment as editor of Roger Alton, the features editor from the Observer's sister title, the Guardian. Alton replaced Will Hutton, who became editor-in-chief of the Observer.
Targett said: "This is a one off chance to revel in two of my greatest passions - magazine journalism and racehorse breeding.
I've been reading Pacemaker, poring over every last page, since I was 12. I hope the racing world will find it more vigorous, more fun and more useful than ever."